mycology (fungi) and parasites test prep

fungi cell type

uni or multicellular eukaryotes

uni = yeast

multi = molds

fungi cell membrane has...

sterols (ergosterol)

cell wall...

chitin

spores present?

yes

fungal diseases

- superficial (localized)

- cutaneous (hair, skin, nails)

- subcutaneous (beneath skin)

- systemic (deep in body)

how are fungi useful to mankind

- used to make antibiotics

- can act as decomposers

- yeast carry out fermentation (making food, bread, wine, etc)

diagnosis of mycoses

1. microscopic exam

2. macroscopic exam

3. fungal culture

4. serology test for host Ab or fungal Ag

1. microscopic examination

- gram stain

- wet prep

- KOH prep

- scotch tape prep

potassium hydroxide preparation

- scraping part of a lesion from skin, hair or nails

- adding drops of KOH

- softens tissue; able to see fungal characteristics

scotch tape preparation

- press sticky side of tape against microbes

- Place a drop of Lactophenol Cotton Blue (LPCB) stain onto a clean glass slide

- look for spores, filaments, etc under microscope

***under BSL-3***

2. macroscopic exam

colony morphology on BAP or Sabouraud Dextrose Agar (SDA)

biochemical tests possible?

not for molds, limited tests for yeast identification

culture yeast vs molds in what temp

y - 35C

m - 25-30C

india ink - C. neoformans

- CSF on slide

- add ink, then coverslip

- 10x, then 40x

- detect capsule "halo"

yeast characteristics

- gram (+)

- reproduce via budding

- large, oval-shaped cells

- nonfilamentous (unicell.)

- produce pseudohyphae -> forms chain of yeast cells

- ferments carbs

molds characteristics

- aerobic growth at 25C

- produce hyphae

hyphae function

nutrition, reproduction, and dispersal of fungi

mycelium

a group or mass of hyphae intertwined

aerial hyphae

grow above the agar surface and produce asexual reproductive spores

vegetative hyphae

grow below agar surface

absorb nutrients

Cryptococcus neoformans diagnosis

- India ink

- fungal culture

- serology

- CSF or serum gram stain

Cryptococcus neoformans treatment (combo**)

amphotericin B

Candida albicans diagnosis

- gram stain

- fungal culture

- wet mount to see germ tube production

Candida albicans treatment

- topical application of miconazole

- oral ketoconazole

- fluconazole for systemic candidiasis

Pneumocystis jiroveci reservoir

soil and human lungs

Pneumocystis jiroveci diagnosis

giemsa stain of lung tissue to see cysts or trophozoites

Pneumocystis jiroveci treatment

Trimethoprim-sulfamethoxazole or TMP-SMX (Bactrim)

dermatophytes

CUTANEOUS INFECTIONS -> infect hair, skin and nails - ringworm / tinea

ringworm treatment

miconazole

ringworm diagnosis

- KOH prep

- fungal culture

dimorphic fungi

Fungi that can exist in two forms

- Sporothrix schenkii

- Histoplasma capsulatum

- Coccidioides immitis

Sporothrix schenckii sign?

small ulcer on arm

Sporothrix schenckii diagnosis

- KOH prep

- fungal culture

- patient's history + signs

Sporothrix schenckii treatment

Itraconazole, oral potassium iodide

transmission of H. capsulatum

inhalation of spores associated with bird or bat droppings

H. capsulatum syndrome

pneumonia or TB like

H. capsulatum diagnosis

- fungal culture

- serology for antigen

- DNA probes

treatment for all systemic mycoses

Itraconazole & Amphotericin B

Aspergillus fumigatus syndrome

growth of mycelium in lungs / fungus ball: pulmonary aspergillosis

- pneumonia like (fever, chest pain, diff. breathing)

- bloody sputum

Aspergillus fumigatus diagnosis

- fungal culture

- KOH prep see branching, septate hyphae and spores

- chest x-ray see fungus ball in lungs

Mucor / Rhizpus disease

Rhinocerebral Mucormycosis

-> infections in paranasal sinuses

Mucor / Rhizpus diagnosis

- Fungal cultures grow a gray cotton candy mold within 4 days

- wet prep

- KOH prep shows aseptate hyphae and spores

parasites - 2 types

protozoa: protists

helminths: worms

intermediate host

species in which the immature form develops (larvae)

definitive host

animal in which the adult parasite matures (adult worm)

protozoa: 2 life cycle stages

a. cyst: round-oval; infecious, dormant stage

b. trophozoite: motile, active stage; reproducing / feeding on host

protozoa reservoirs

- animal normal flora

- soil

- water

Giardia duodenalis transmission

ingest cysts

fecal-oral

Giardia duodenalis diagnosis

- microscopic exam of stool for trophozoites or cysts

- serology of Ag in stool (ELISA, FA)

Giardia duodenalis treatment

metronidazole (antiprotozoal medication)

oral rehydration

Trichomonas vaginalis diagnosis

- wet mount

- DNA probes

- Ag serology

Trichomonas vaginalis treatment

metronidazole

Plasmodium diagnosis

- microscopic exam of ring stage of Plasmodium

inside red blood cells in Giemsa or Wright stained thick and thin blood smear

malaria syndrome

- splenomegaly and hepatomegaly

- chills, night sweats, fever

- vomiting

- headache

- hemolytic anemia

In the life cycle of Plasmodium, the mosquito is the definitive host because

sexual reproduction (fertilization) and the formation of sporogony (sporozoites) occur within its body

It harbors the adult sexually reproducing stage

Plasmodium treatment

Chloroquine

Artemisinin

Toxoplasma gondii transmission

ingest oocyst

congenital (can cause meningitis, neurological problems, or still birth :( )

toxoplasmosis syndrome

in immunocompromised:

- brain lesions

- swollen lymph nodes

- hepatitis

Toxoplasma gondii diagnosis

- serology / immunofluorescence

for Ab (in serum)

Toxoplasma gondii treatment

pyrimethamine

Cryptosporidium diagnosis

- microscopic exam of stools for oocysts

- acid-fast stain

- serology

cryptosporidiosis syndrome

after a week...

- 9-12 day massive diarrhea

- dehydrated (shock if prolonged)

- stomach cramps, vomiting, fever, nausea...

Cryptosporidium treatment

- oral and electrolyte rehydration

- Nitazoxanide

cestodes - tapeworms

Scolex—head that has suckers for attachment

Absorb food through cuticle

Proglottids—body segments; contain male and female reproductive organs

Enterobius vermicularis causes...

pinworm infection

reservoir for pinworm, hookworm and giant roundworm (Ascaris)

humans (definitive host)

environment, soil

Enterobius vermicularis transmission

ingest eggs

- easily stick to hands or surfaces

Enterobius vermicularis syndrome

- perianal itching

- insomnia

- eosinophilia

- irritability

- weight loss

Enterobius vermicularis diagnosis

scotch tape method

treatment for pinworm, hookworm and giant roundworm (Ascaris)

mebendazole

Necator americanus causes...

hookworm infection

Necator americanus transmission

larvae penetrate skin with its "cutting plate" mouth

wear shoes

endemic in southeastern US

Necator americanus syndrome

- dermatitis (skin irritation)

- iron deficiency anemia

- diarrhea

- pneumotitis

- eosinophilia

Necator americanus diagnosis

see eggs in stool

Ascaris lumbricoides syndrome

Ascariasis

- hepatitis

- malnutrition

- eosinophilia

- jaundice

- intestinal obstruction

prevalent in tropical areas that lack sanitation and good hygiene practices

Ascaris lumbricoides transmission

ingest eggs / ova

Ascaris lumbricoides diagnosis

eggs / worm in stool

Taenia solium transmission

ingesting cysticerci or larval forms in raw pork

Taenia solium syndrome

Neurocysticerosis

-> weight loss

-> headaches

-> epileptic seizures

Ophthalamic Cysticerosis

-> vision impairment

Taenia solium diagnosis

eggs or proglottids in stool

brain MRI

Ab serology

Taenia solium treatment

praziquantel or niclosamide drugs or surgical removal of cysticerci from brain